Sander



SANDER Filed June '7, 1940 4 Sheets-Sheet 1 4- l n so '75 nswm ISnbentor (Ittornqis c. A. CAMPBELL 2,243,244

SANDER Filed June 7, 1940 4 Sheets-Sheet 2 3 m If 1: 691mm,

(Ittornegs May 27, 1941.

May 27, 1941.

C. A. CAMPBELL SANDER Filed June 7, 1940 4 Sheets-Sheet 4 VIII/711A IBP attorneys Patented May 27, 1941 SANDER- Charles A. Campbell, Watertown, N. Y., assignor to The New York Air Brake Company, a corporation of New Jersey Application June '7, 1940, Serial No. 339,387

25 Claims.

This invention relates to sanders for high speed railroad trains.

The high braking ratios used on high speed trains have led to the use of sanding ahead of every braked unit (usually ahead of every truck), at least in the heavier applications, such as emergency applications. The important thing in any such system is to make certain that such sanding at every unit will become effective before the brake application for that unit becomes effective. If sanding precedes the brake application, wheel sliding will rarely occur. If the brake application precedes sanding, wheel sliding is likely to occur and, having started, will continue despite sanding, which then greatly increases the damage done to the wheels.

In prior applications I have described sanding systems in which a series of pneumatic sander relays throughout the length of the train are controlled in unison from a control unit at the head of the train, the control preferably being electrical. Such control systems give timed sanding which may be initiated manually or as the result of the emergency response of some portion of the brake mechanism at the head of the train. They afford a re-set mechanism by which timed sanding, however initiated, may be terminated. They afford sanding at will, and in certain embodiments sanding at will is limited to the propelling units.

There are obvious advantages in this unified sander control; in fact its flexibility cannot be approached by any other known system of sanding throughout a train. As heretofore embodied it had one disadvantage- When an emergency application was initiated near the rear of a train so equipped, either by the operation of the conductors valve or by the rupture of the brake pipe, the effective brake application started on the rear units of the train and progressed serially from the rear to the front of the train. The sander mechanism could not respond until the emergency braking action reached the head of the train. Hence the rear brakes, under these conditions, would apply before their sanders went into action.

The present invention imposes no limit on the use of the head end control systems heretofore developed. In fact it can be embodied in any such systems without requiring material change. The invention centers around the use of a highly efiective large capacity pneumatic sanding relay on each vehicle, such sanding relay having an electrical controlling means in the train circuit controlled from the head end station as heretofore, and a functionally independent local pneumatic controlling mechanism responsive to the initiation of emergency braking conditions on the corresponding vehicle. This pneumatic controlling mechanism may conveniently be connected to the sanding port of a brake-controlling valve device, such as a D-22 control valve and operates so rapidly as to anticipate effective braking. The control includes a timing mechanism set for a very short time period.

When any brake controlling device makes an emergency response, it operates through the pneumatic control to cause the corresponding sanding relay to move to sanding position and remain there for a time period sufficient to permit the emergency brake application to progress to the head of the train and affect the front-end sander control. When this occurs the frontend electric control of sanding takes efiect as to all the pneumatic sanding relays on the train without interference by the local pneumatic con trols. Almost immediately, the local pneumatic controls cut out. Consequently the local pneumatic controls do not inhibit the operation of the re-set mechanism, except during the very short time period for which they are set. Thus the flexibility of front-end control is not ,materially affected.

In short, all the advantages of head end control are combined in a very simple manner with the advantage inherent in local sander control exercised by each brake controlling valve device. The relay is also adaptable to other uses, as will be explained, I

A practical embodiment of the invention will now be described in detail by reference to the accompanying drawings.

Figure 1 is a diagram of the brake system and the sander system on the leading or propelling unit.

Fig. 2 is a similar diagram of the brake system and sander system on the second and all succeeding units. Figs. 1 and 2, when assembled from left to right in the order stated, form a diagram for the first two units of a train.

Fig. 3 is a sectional view of an intercepting valve used between the supply reservoir of the brake system and the sanding reservoir of the sanding system on the second and all succeeding units.

Fig, 4 is a diagrammatic section of the relay valve with its electrical and pneumatic controls. The parts are shown in running (inactive) position..

Figs. 5, 6 and 7 are diagrams of the slide valve components of the relay showing, respectively, preliminary cleanout position, sanding position and final clean-out position.

Fig. 8 is a section of a sanding valve suitable for use in controlling the system.

Fig. 9 is a diagram showing how the relay may be connected with a braking system for simple pneumatic control.

A two-car unit is illustrated in Figs, 1 and 2 because this offers the simplest way to explain the controlling principles of the invention. The delay in propagation of an emergency application through two cars is so slight that the advantages of the invention hardly reach significant proportions in such ashort train, but repetition of Fig. 2 in the drawings would complicate the drawings without adding anything to the disclosure. It is within the contemplation of the invention to duplicate the unit of Fig. 2 on the third and all succeeding cars of trains of any practicable length, and the importance of doing so increases rapidly with the length of the train.

Since the relay is the heart of the invention, an understanding of the construction of the relay is desirable before the system aspects are discussed.

The type of sand trap to be controlled by the relay determines the porting of the relay. It will suffice for preliminary purposes to explain that the preferred sand trap has two air connections, a sanding air line which furnishes air to operate an ejector and supply sand through the sand pipe to the track, and a clean-out air line which, when placed under pressure, disconnects the sand pipe from the sand trap and subjects the pipe to pressure to blow it free of any obstructions.

The relay valve, in going into action, performs a cycle of short but appreciable duration, in which air is first furnished to the clean-out and sanding air lines and then cut off from the cleanout line, which is then vented, while air continues to be supplied to the sanding air line. On the return'excursion of the relay, which also takes a short but appreciable interval of time, air is first cut off from the sanding air line and then the clean-out line is Subjected to a short cleanout blast for the purpose of clearing the sanding pipe completely as it goes out of action. After this, both lines are vented.

The pilot valve of the Sender relay is a slide valve having ports of limited capacity, and these pilot the operation of large capacity supply and vent poppet valves which control the flows to the sanding and clean-out air lines. In this way large capacity flow to the sander is had without requir ing the use of alarge slide valve.

Fig. 4 is a diagram, in which the positions of the ports and the mechanical components have been modified slightly so as to bring all the ports into a single plane, to the end that they may be traced in a single view.

The entire relay is carried on a pipe bracket I I which is supported on the car and to which all pipe connections are made. The sanding air line appears at l2, the clean-out air line at l3, the sanding supply reservoir connection, which furnishes all operating air, at It, and the timing reservoir connection at 5. The connection [6 is from the sanding port of the control valve, as will be explained, and is the connection through which the relay is put into action by emergency response of the control valve. Leading from the connections I2 to it inclusive are freely communicating passages formed in the bracket and in the connected housings. For the purpose of reducing the number of reference numerals and simplifying the tracing of ports, these interconnected ports and pipes are considered as forming continuous passages and are given a single reference numeral. In addition to the passages which form continuations of the pipes 52 to is inclusive, the bracket and connecting housings are formed with an exhaust port El, and the bracket H encloses a chamber H! which participates in a timing function hereinafter described.

Mounted on one side of the bracket H is a housing i9 which encloses the pilot slide valve mechanism of the relay as well as the piloted poppet valves. In the upper portion of the housing 59 are mounted a slide valve chamber bushing 2| and a cylinder bushing 22. Working in the cylinder 22 is a piston 23 which has a stem 24 extending into the slide valve chamber within bushing 21 and terminating in the spider 25 which guides the stem. Mounted for lost motion between the shoulder 26 adjacent the piston and the spider 25 is the main slide valve 27. This has wings 23 which straddle the piston. stem 24 and which carry a bow spring 29 arranged to hold the valve 21 against its seat. Between the wings 28 the back of the slide valve 2'! is formed with a seat for a graduating slide valve 3|, which is closely confined between the shoulders 32 and 33 on stem 24 so that the graduating valve partakes of all of the movements of the piston 23.

Piston 23 is urged to the right by a duplex spring assembly so arranged that only one of its two concentric springs resists the motion of the piston to the left through that part of its travel corresponding to the lost motion of the piston relatively to the main slide valve 21. At the limit of such motion both springs oppose motion of the piston.

The main or primary spring is shown at 34 and is confined under stress between an inner spring seat 35 and an outer cupped spring seat 35. These two spring seats are connected together by a headed stem 31 which is slidable through a bushinig 38. This in turn is slidable axially through the spring seat 35 for a limited range corresponding to the lost motion just mentioned. The spring seat 35 seats within the end of a closure cap 39 which closes the outer end of the cylinder 22. The cap is sealed by a gasket, as shown, and the gasket projects inward far enough to serve as a seat for the piston when the latter arrives at the outer limit of its motion.

The secondary spring 4| is a lighter spring mounted concentrically within the spring 34. It is sustained at its inner end on the spring seat 35 and is sustained at its outer end on the cupped spring seat 42, which is thimble-like in form, engages the end of bushing 38 and telescopes over the spring seat 35. Its telescoping motion is limited by the bushing 38. The action is as follows: When the piston 23 moves outward, it is opposed initially by the spring 34 until the spider 25 engages the slide valve 21 and is about to move it. At this point bushing 38 and spring seat 42 reach their limit of motion. From then on the resistance of the inner spring M is added to that of the spring 34. The purpose is to cause the piston to pause momentarily at the limit of motionof the graduating valve it! relatively to the slide valve 21. This effect is had in both directions of motion.

The space within valve chamber bushing 2| and to the right of the piston 23 is in free communication with the sanding reservoir passage I4. It is also in communication, by way of filter 43 and choke 44, with a passage 45 in bracket H and communicates with the chamber !8 already described. From the space within the cap 39 to the left of piston 23, a passage 46 leads through the body I9 and bracket II, as shown.

In the seat on which the main slide valve 21 is mounted are three ports; a clean-out air control port 41, a branch of the exhaust port i1, and a sanding air control port 48. In the valve 21 and communicating with the port 43 in all positions of the slide valve is a through port 49. An enlargement at the bottom of the port 49 is the means to maintain communication between it and the port 48 in all positions of the slide valve 21. Also formed through the slide valve 21 is a port which is enlarged at its bottom so that it communicates with the exhaust port 11 in all positions of the slide valve. This port has an extension 52 leading outward and thence to the graduating Valve seat. in the back of the slide valve. In addition there are two impulse ports 53 and 54 which lead through the slide valve.

The graduating valve has two cavities in its lower face, namely 55 and 56, and has drilled through it an impulse port 51.

These ports are so arranged that in the normal or running position of Fig. 4 clean-out control port 41 is connected to exhaust port I1 by way of port 53 and cavity 55, port 52 and port 5|. At the same time the sanding air control port 48 is connected to exhaust port 11 by port 49, cavity 56 and port 5!, and port 51 communicates with the port 45 which is then blanked at the seat.

When the piston starts outward the graduating valve 3| exposes port 49 at the same time that port 51 opens to port 53 and the ports are fully open at the limit of lost motion of the graduating valve relatively to the slide valve. The efiect is to admit air under pressure from the sanding supply reservoir to both the ports 41 and 48 (see Fi 5).

The remaining movement of the piston 23 outward moves the slide valve and carries port 53 out of register with port 41, cutting oii the flow of air to port 41 and causing port 54 to register with port 41 (see Fig. 6).

On the return excursion the graduating valve first closes the port 49 and then the port 51 registers briefly with the port 54 (see Fig. 7 to furnish a brief clean-out blast to the port 41. As above set forth, the piston pauses momentarily in the position of Fig. '7 because at this point the spring 4| reaches its limit of expansion. Continued movement carries the slide valve inward so that port 54 moves out of register with port 41. When running position (Fig. 4) is reached, both ports 41 and 48 are vented to atmosphere by connection with port 11 as already described.

Mounted in the lower part of the housing l9 are the two poppet valve mechanisms which are controlled by the admission and exhaust of pressure fluid to and from the ports 41 and 48 respectively.

Port 41 leads to the space within the cap 8i and beneath the flexible diaphragm $2, the diaphragm being clamped at its periphery between the cap BI and the housing 19 and connected at its center to a thrust plate 63 which carries an exhaust poppet valve 64. The space immediately above the diaphragm 62 is connected to atmosphere by way of port 11.

When the diaphragm is in its normal lower position the valve 64 is open and connects the chamber 65, to which the clean-out air line 13 leads, with atmosphere. When pressure fluid is admitted beneath diaphragm 62 the efiect'is to force the valve 64 upward, closing the exhaust passage. A lug on the end of the valve 64 strikes a similar lug on the lower end of a poppet valve 56 and unseats this valve against the opposition of a coil compression spring 61 and fluid pressure communicated from the sanding supply reservoir line I4 to the chamber 68 above the poppet valve 66.

Similarly, the sanding control port 48 leads to the space within cap H and beneath flexible diaphragm 12. This is clamped at its periphery between the cap 1| and the housing l9 and is clamped at its center to the thrust plate 13, to which the exhaust valve 14, similar to the valve 64, is attached. The chamber is connected to the sanding air line 52 and the valve 14 carries a lug which, when the valve is forced closed, strikes a similar lug on the inlet valve 16 and forces it upward against the resistance of the coil compression spring 11 and the pressure communicated to the chamber 18 by the sanding supply passage l4.

Thus the two passages I2 and 53 are normally vented to atmosphere by the poppet valves 64 and 14. If the port 41 is put under pressure, the exhaust passage is closed and a direct connection is open past supply valve 55 to the passage l3. Similarly, if the passage 48 is under pressure, the exhaust passage past the valve 14 is closed and the valve 15 is unseated to admit air from the sanding reservoir connection directly to the sanding connection i2. In this way a relatively small slide valve mechanism, with ports of comparatively small size, pilots the action of inlet and exhaust mechanisms of large capacity.

Electric control is exercised by energizing and deenergizing a winding 8| which is mounted under a cap 82 on a valve body 83 bolted to bracket H. free communication by way of port 45 with the chamber 18 already described. The port 45 leading from the space to the left of piston 23 terminates in valve chamber 85. In the chamber 85 is a double beat poppet valve having an exhaust head 86 which coacts with an atmospheric exhaust seat 81 and an inlet head 88 which coacts with the supply seat 89 controlling flow between the chambers 84 and 85.

A coil compression spring 9| urges the poppet valve toward the exhaust seat. When the winding BI is de-energized, as it is under running conditions, the exhaust head 86 of the double beat valve seals in seat 81 and the port 45 is connected by way of chamber 84 and port 45 with the chamber l8, and further by way of choke 44 and filter 43 with the slide valve chamber within bushing 2|. As explained, this chamber is in free communication with the sanding supply reservoir line l4. Thus, under normal conditions, the pressures on the two sides of the piston 23 equalize and the springs force the piston 23 to its innermost or right-hand position, shown in Fig. 4.

If the winding BI is energized, the double beat poppet valve is moved downward, isolating chamber 85 from chamber 84 so the chamber I8 remains charged, and connecting chamber 85 with atmosphere through a flow connecting choke 92. It follows that the space to the left of piston 23 is vented to atmosphere at a rate controlled by the flow capacity of choke 92. The piston moves outward against the resistance of spring 34 and just at the limit of lost motion between the piston and the main slide valve 21 In the housing 93 is a chamber 84 which is in the resistance of the second spring M is added, so that the piston pauses momentarily in that position and then resumes its outward excursion until it seals on the cap gasket. This is sanding position.

When the winding 8! is die-energized, the double beat poppet valve 86, 88 will return to the position shown in Fig. 4, closing the exhaust from chamber 85 and connecting chamber 85 with chamber 84 and chamber I8. The resulting increase of pressure on the outer face of piston 23 will start the return excursion of the piston. Under these conditions the choke 44 will exert control on the rate of development of pressure on the left side of piston 23 and. consequently on the rate of inward motion of the piston.

The structure indicated at 93 is merely a separable connector for the leads 94 and 85, which are connected with the terminals of the winding BI.

Bolted to the bracket 4! is a housing 56 which contains a chamber 91 connected to the exhaust passage I7, and a chamber 9.3 connected to the timing reservoir connection. E5. A timing reservoir is indicated at 89 in Figs. 1 and 2 and augments in any desired degree the volume of chamber 98. The connection iii leads to a chamher I!!! within the cap Hi2 and below a diaphragm 1833. This is clamped at its periphery between body 95 and cap 582 and is connected at its center to the thrust plate I54. Slidably mounted within the thrust plate IM and limited in its outward motion by a stop flange is a plunger I95 which is urged outward by the coil compression spring IE5. plunger see reacts against an exhaust poppet valve If to urge it in an exhaust closing direction. The pilot of the exhaust valve IQ'I is in position to collide with the pilot of the reversely seated poppet valve I63, which is urged close-cl by a coil compression spring Hi9 and which controls flow from the chamber !3 previously described to the chamber 93 and connected timing reservoir 89. The flow is by way of a choke III and ball check valve I12 to the chamber H3 behind the valve I98.

The connection It leads from the sanding port of the brake controlling valve device and. when pressure is developed in connection !6 the diaphragm Hi3 moves upward, forcing the valve I! closed and the valve IGB open. The effect is to reduce the pressure in the chamber I8 and since this is normally connected by way of port 45, chamber 84, chamber 85 and port at, with the space to the left of the piston 23, the resulting reduction of pressure in chamber I8 causes the piston 23 to move outward.

This reduction of pressure will continue until timing reservoir 99 is charged nearly to equalization with the sanding supply passage I4. Choke 64 feeds to chamber I8 at a rate less than the outflow through the larger choke IlI, at least until reservoir 99 is nearly charged. Ultimately, development of pressure in chamber I8 would cause piston 23 to move inward and terminate sanding. This would occur after a short interval, say ten seconds, which is sufiicient to span propagation of emergency braking from the rear to the front of a long train.

Normally the winding 8| is energized by emergency response at the head of the train before the end of this time interval, and the resulting shift of valve 88, 88 cuts the mechanism in housing $6 out of control. The latter then simply completes its timing cycle by charging reservoir When the diaphragm its is forced upward,

99 while the front end control maintains sanding for the longer (say ninety second) period for which it is set. After charging of reservoir 99 has occurred, de-energization of winding 8| will terminate sanding without interference by the mechanism in housing 96, even though connection I5 be still under pressure.

While the mechanism in housing 96 is active for the ten second period, sanding cannot be terminated from the head of the train. Except for this the electric control is always effective to stop sanding and it is always effective to start sanding or to maintain sanding started by the controller in housing 96.

The above being the construction and operation characteristics of the sander relay, reference is made to Figs. 1-3 for a typical installation availing of the dual control afforded by the relay. Control valves of the D-22 type are shown and these may be used in an automatic, or a combined straight air automatic system, but since emergency applications originating at the rear end of the train are propagated on the automatic side, it is sufficient and simpler to disclose an automatic system.

The main reservoir appears at M5, the brake valve at IE6 and feed valve at ill. The brake valve is assumed to be of equalizing discharge type with equalizing reservoir H8 and would ordinarily have release, running, lap, service and emergency positions. In the last named position it completely vents the brake pipe which is shown at H9. A branch I2I with double heading cock I22 connects the brake valve with the brake pipe. The brake pipe extends from end to end of the train and is connected from car to car by hose I23 with separable connections IZd. Angle cocks I25 are used at each end of each unit, and conduct-ors valves are provided to permit local venting of the brake pipe. One conductors valve is shown at I20 in Fig. 2.

A branch I26 of the brake pipe IE9 on each car leads through a normally open-stop cock and a dust collector to a brake controlling valve device I27, capable of operating on the automatic principle and serving in emergency position to supply air under pressure to sanding connection IS. As typical, the valve device I2? is illustrated as a 13-22 control valve, standard in the air brake art. This has three connections to chambers in a multi-chambered reservoir I28, I29 being the auxiliary reservoir connection, iC-lI the emergency reservoir connection and I32 the displacement volume connection.

It should be stated that connection I32 and the displacement volume are under pressure during brake application, and vented at other times, as will be readily understood by persons skilled in te brake art.

The brake pipe H9 is normally under pressure (say lbs. per sq. in.) and the valve I2'I functions in release position to supply charging air to the auxiliary and emergency reservoirs and to a supply reservoir connection I33. On the head end unit braking air is furnished by the main reservoir, so in that unit connection I33 charges only the two sander supply reservoirs I34 through pipe I35 (see Fig. 1). On trailers however (see Fig. 2) connection I33 charges the brake supply reservoir I36 through pipe I31, and then the sander supply reservoir i34-T is charged from reservoir I35 through an intercepting valve I38 (see Figs. 2 and 3).

From brake supply reservoir I36 a pipe I39 leads to the body of intercepting valve I38 and from this another pipe MI leads to sanding supply reservoir I34-T. A choke I42 limits the rate of flow through pipe I39 to assure preferential charging of reservoir I36. The pipes I39 and I'4I lead to ports in the seat of a slide valve Hi3, which has a cavity normally connecting these ports (see Fig. 3). A spring I44 biases the valve to connecting position from which it is forced by diaphragm motor I45 when the latter is subjected to pressure. A branch of pipe I32 connects the working space of motor I45 with the displacement volume so the sanding reservoir I3l-T cannot rob reservoir I36 of air during a brake application, because development of pressure in the displacement volume during braking closes the intercepting valve.

The spring device IE8 is merely means to hold the slide valve I43 to its seat.

Various equivalent intercepting arrangements will readily suggest themselves. The valve i21, in response to reduction of brake pipe pressure, establishes related pressures in pipes Hi1 leading to admission and exhaust relays Hi8, which function to establish proportionate pressures in pipes I43 and connected brake cylinders I5I. The relay M8 on the motor unit derives its air supply via pipe I52 from main reservoir II5, but on trailers the relays [48 derive braking air from a branch of pipe 431 and hence from the corresponding local supply reservoir I35. This is desirable because the motor unit has more sander heads to supply and the main reservoir is readily available for the brakes.

The head end of the motor unit is shown provided with two brake cylinders EM and four sets of sanding traps I53 appropriately connected to the clean-out air line 53 and the sanding air line I2. The structure of the sand traps is not important provided they are suited for the stated clean-out and blast sanding functions, but those outlined in the drawings are shown as conforming to the disclosure of my application Serial No. 314,172, iled January 16, 1940. Similar sand traps 553 are mounted on the trailing unit. The particular structure of the sand traps is not a feature of the invention. The relay described is ported to serve traps of this particular type, but might otherwise be ported within the scope of the invention, which relates primarily to the control of the relay rather than the specific functions of the relay itself.

The pipes I5 which lead from the sanding connections of the control valves I21 are each connected to a corresponding sanding relay'so that each relay will respond to an emergency function of the corresponding control valve I21. The pipe I5 on the head end unit is also connected to an impulse valve I54 (see Fig. 1). This impulse valve comprises a diaphragm I55 which is urged by coil compression spring I55 against the valve seat I51. Pressure arriving by the pipe !5 acts on the diaphragm valve I55 in a valve opening direction and the arriving pressure is further communicated to the space behind the valve by restricted connection 53. Thus when pressure is first delivered to the pipe It the diaphragm valve I55 opens and delivers air under pressure to the outlet pipe I53 which leads to the main sander control valve I55. However, as

soon as the space behind the diaphragm I55 is charged, the diaphragm valve closes and upon its closure a choken I52 becomes effective to vent the pipe I53 to atmosphere.

The mechanism just described is a known impulse valve and is illustrated as one convenient he. depresses the button I13.

way to deliver a short pressure impulse to the motor element of the valve IBI, even though pressure in the pipe I6 be maintained continuously throughout a sustained emergency application.

The main control valve Ifil of the sanding system is of the type described and claimed in my allowed application Serial No. 266,819, filed April 8, 1939. The internal construction of the valve I'5I is clearly shown in Fig. 8 and is not specifically claimed herein. Consequently its operation will be traced without unduly detailed discussion of the structure.

A timing reservoir I33 is connected to the body iEI by pipe I54 and determines the duration of timed sanding effected by the valve IIiI. The usual setting is for about 90 seconds to span the longest probable stopping time. The valve is set for timed sanding in either of two ways; by the admission of air through the pipe I53 under the control of the head end control valve I21, or by depression of the timed sanding button I55. In either case the piston I35 is moved down full stroke and shifts the balanced piston valve I to its lowermost position, carrying with it a timing piston I51 against the resistance of the coil compression spring I58.

In running position of the valve the timing reservoirl53 is charged to supply reservoir pressure by way of the connection I35, the reduced middle portion of the valve I55 and the pipe I34. When the valve I56 is moved full stroke downward, the supply connection I35 is disconnected from the timing reservoir I53 and the latter is connected by pipe I54, the reduced middle portion of the valve IE5, with the pipe I58 which leads to the motor I59 of the sanding switch hereinafter described. At the same time the timing reservoir is connected with a port I1I which establishes a holding pressure on the piston H51 and with choke I12 controlling an atmospheric vent. Consequently the piston I31 remains in its lowermost position until the pressure fluid in the timing reservoir bleeds away through the choke I12 provided for that purpose.

If it is desired to terminate sanding sooner, this may be done by depressing the sanding at will button I13 which opens the valve I14 and admits pressure from the connection I35 below the piston 851. This forces the piston upward full stroke. When it arrives in its uppermost position a vent port I18 dissipates the pressure below the piston I51. It is also possible to sand at will by pressing and holding the button I13. This admits air below the piston I61, the air flowing past the piston through the port Ilil to the connection I58.

The motor I69, when subjected to pressure, closes the contactor I86 of a normally open switch against the contacts I14 and I15. A spring biases the contactor to circuit breaking position. Thus if pressure be admitted through the pipe I59, or if the button I60 be depressed, the switch will be closed for the chosen time period, assumed to be 90 seconds. If the engineer wants to stop sanding short of that period, At other times if he wants to sand for a short period, he presses button I13 and holds it in as long as he wants sanding to continue. The effect of the latter operation is to hold the switch closed as long as the button I13 is held closed.

The switch merely closes the circuit between the lines I15 and I11, which includes the battery H3 and extends throughout the train, the train line being connected from car to car by jumpers, one of which appears at I19 in Fig. 2. The leads 94 and 95 of windings 81 are bridged across the train lines so that the effect of closing the switch is merely to energize all the windings 8| simultaneously.

In any emergency application, Wherever produced, the response of each control valve I21 will put the pneumatic controller in housings 96 of each sanding relay into operation, and this will serve to put the corresponding sanders into operation and maintain them in operation for ten seconds. If the emergency application starts at the head of the train, the valve I54 will deliver a motive impulse to the sander control valve IGI and by thus setting it for limited sanding will put all the sanders in operation by energizing the windings 8|. This becomes effective as soon as, or before, the mechanisms in housings 96 become effective. With an emergency application starting at the rear end of a long train the mechanisms 95 at the rear of the train Will become effective before the sander valve IGI is operated. Under such conditions sanding will start at the rear as soon as, or sooner than, the emergency application becomes effective on those cars and before the valve IGI responds.

Any sanding operation produced by manipulation of the buttons I60 and I13 will be electrically controlled without the response of the pneumatic mechanisms in the housing 96. If the pneumatic device should go into action first, for any cause, the electric control simply takes over and the pneumatic control concludes its ten second timing cycle without further effect on the sanding relay. If the electric control be active and the pneumatic control in any housing 96 thereafter becomes active, the electric control isolates the pneumatic control from the relay and the pneumatic control performs its timing cycle .impotently. Thus the two controls are wholly distinct, and neither interferes with the other, except that it is impossible to terminate timed sanding electrically while the pneumatic control is going through its timing cycle.

Modification The relay device above described is available for general use because it can be controlled electrically without the pneumatic mechanism in housing 96 (which, in such case, would be blanked off) and it can be controlled pneumatically without the electrically actuated mechanism in housing 83.

In Fig. 9 a strictly pneumatic scheme is disclosed by way of example. In such a system it is convenient to use the D2? control valve with the sander relay connected with the sanding pipe I6--P.

Consequently in Fig. 9 those parts which are identical with parts in Figs. 1 to 8 are given the same numeral with the distinguishing letter P. The changes are as follows: In place of the housing 83 a blanking plate I8I is provided. This has a loop port I82 which connects the ports $P and G5P. It is shown as also blanking the atmospheric port Il-P, but this is obviously a matter of choice because the port is elsewhere connected to atmosphere. The bracket IIP and the mechanisms in the housings 95P and I9-P are unchanged. The timing reservoir 99-1 is of larger volume to afford a time interval, of say 90 seconds, sufficient to span an emergency stop. The sander supply reservoir I34-P may be charged in any suitable way, a

convenient means being a pipe I83 leading from the reservoir of the water raising system. I prefer this to the schemes shown in Fig. 2, but, if desired, that scheme could be embodied exactly as shown in Fig. 2.

In any case where the housing 95 is omitted, the connections I5 and I6 would be omitted because functionless. It is obviously unnecessary to blank the exposed end of the atmospheric port II, but it is important to blank the choke I II so as to pervent loss of air from the reservoir I8. In other Words, any blanking plate or plug that would close the port I II could be used.

Thus the invention provides a relay with two controls, one electrical and the other pneumatic, either or both of which may be used. It makes use of a slide valve mechanism of small size to pilot poppet valve mechanisms of large flow capacity. In this Way a small, light, slide valve mechanism can be used, one that will function with extreme rapidity and precision without requiring the use of substantial volumes of compressed air.

A number of uses for the relay have been suggested and others are obviously possible. Thus the description is intended to be illustrative rather than limiting, the scope of the invention being defined solely by the claims.

I claim:

1. The combination of a pneumatic train braking system comprising braking units at intervals throughout a train, a brake pipe connected therewith, and means associated with the brake pipe at diilerent points in the length thereof for causing brake applications; a train sanding system comprising sanding units, each associated with a corresponding braking unit throughout the train; and two independent means by which operation of the sanding system is caused to occur as an incident to brake application, the first comprising local connections from each braking unit to corresponding sanding units serving to start and for a short interval to maintain sanding by such sanding unit as an incident to braking response of the braking unit, and the second comprising a master controller and connections therefrom to the various sanding units, and means for actuating the master controller as an incident to a brake applying function of the braking system at the head of the train.

2. The combination of a pneumatic train braking system comprising braking units at intervals throughout a train, a brake pipe connected therewith, and means associated with the brake pipe'at different points in the length thereof for causing brake applications; a train sanding system comprising sanding units, each associated with a corresponding braking unit throughout the train; two independent means by which operation of the sanding system is caused to occur as an incident to brake application, the first comprising local connections from each braking unit to corresponding sanding units serving to start and for a short interval to maintain sanding by such sanding unit as an incident to braking response of the braking unit, and the second comprising a master controller and connections therefrom to the various sanding units, and means for actuating the master controller as an incident to a brake applying function of the braking system at the head of the train; and manually operable means for actuating said master controller independently of the braking system.

3. The combination of a pneumatic train braking system of the automatic type having an emergency application function and comprising automatic brake valve units at intervals throughout a train, a normally charged brake pipe connected therewith, an engineers brake valve for normally controlling brake pipe pressure and means operable to vent the brake pipe at various points throughout the length thereof to produce emergency reduction of brake pipe pressure; a train sanding system comprising sanding units each associated with a corresponding brake valve unit throughout the train; and two independent means by which operation of the sanding system is caused to occur as an incident to an emergency reduction of brake pipe pressure, the first of which comprises local connections from each of the automatic brake valves to corresponding sanding units, serving upon emergency response of a brake valve to actuate the corresponding sanding unit for an interval at least as long as the time of propagation of an emergency reduction of brake pipe pressure from end to end of the brake pipe, :and the second comprising a master controller, controlling connections therefrom to the various sanding units, and means for actu ating said master controller as an incident to emergency reduction of brake pipe pressure at the head of the train.

4. The combination of a pneumatic tnain braking system of the automatic type having an emergency application function and comprising automatic brake valve units at intervals throughout a train, a normally charged brake pipe connected therewith, an engineers brake valve for normally controlling brake pipe pressure and means operable to vent the brake pipe at various points throughout the length thereof to produce emergency reduction of brake pipe pressure; a train sanding system comprising sanding units each associated with a corresponding brake valve unit throughout the train; and two independent means by which operation of the sanding system is caused to occur as an incident to an emergency reduction of brake pipe pressure, the first of which comprises local connections from each of the automatic brake valves to the corresponding sanding units, serving upon emergency response of a brake valve to actuate the corresponding sanding unit for an interval at least as long as the time of propagation of an emergency reduction of brake pipe pressure from end to end of the brake pipe, and the second comprising a master controller, controlling connections therefrom to the various sanding units, means for actuating said master controller as an incident to emergency reduction of brake pipe pressure at the head of the train, and means for maintaining said master controller in sanding position for a period at least as long as the duration of an emergency stop.

5. The combination of a pneumatic train braking system of the automatic type having an emergency application function and comprising automatic brake valve units at intervals throughout a train, a normally charged brake pipe connected therewith, an engineers brake valve for normally controlling brake pipe pressure and means operable to vent the brake pipe at various points throughout the length thereof to produce emergency reduction of brake pipe pressure; a train sanding system comprising sanding units each associated with a corresponding brake valve unit throughout the train; two independent means by which operation of the sanding system is caused to occur as an incident to an emergency reduction of brake pipe pressure, the first of which comprises local connections from each of the automatic brake valves to the corresponding sanding units, serving upon emergency response of a brake valve to actuate the corresponding sanding unit for an interval at least as long as the time of propagation of an emergency reduction of brake pipe pressure from end to end of the brake pipe, and the second comprising a master controller, controlling connections therefrom to the various sanding units, means for actuating said master controller as an incident to emergency reduction of brake pipe pressure at the head of the train, and means for maintaining said master controller in sanding position for a period at least as long as the duration of an emergency stop; and manually operable means for suspending the action of said maintainin means.

6. The combination or" a pneumatic train braking system of the automatic type having an emergency application function and comprising automatic brake valve units at intervals throughout a train, a norm-ally charged brake pipe connected therewith, an engineers brake valve for normally controlling brake pipe pressure and mains operable to vent the brake pipe at various points throughout the length thereof to produce emergency reduction of brake pipe pressure; a train sanding system comprising sanding units each associated with a corresponding brake valve unit throughout the train; two independent means by which operation of the sanding system is caused to occur as an incident to an emergency reduction of brake pipe pressure, the first of which comprises local connections from each of the automatic brake valves to the corresponding sanding units, serving upon emergency response of a brake valve to actuate the corresponding sanding unit for an interval at least as long as the time of propagation of an emergency reduction of brake pipe pressure from end to end of the brake pipe, and the second comprising a master controller, con-trolling connection-s therefrom to the various sanding units, means for actuating said master controller as an incident to emergency reduction of brake pipe pressure at the head of the train, and means for maintaining said master controller in sanding position for a period at least as long as the duration of an emergency stop; and manually operable means for suspending the action of said maintaining means and manually operable means for shifting said controller to sanding position independently of said brake system.

7. In a sander relay the combination of a sander valve having a sanding position, and a running position in which sanding is suspended;

a movable abutment connected to shift said valve between said positions; means forming a Working space at one side of said abutment; force-developing means associated with said abutment for biasing said abutment and valve toward running position when said working space is charged with fluid under pressure above a definite value and toward sanding position when said pressure is substantially reduced; a delay chamber; means for charging said delay chamber with pressure fluid at a restricted rate; primary controlling means normally connecting said working space and said delay chamber, but operable to isolate them from each other and connect the Working space to exhaust; a timing chamber; and secondary controlling means normally connecting the timing chamber to exhaust but operable to close said exhaust and connect the timing and delay chambers together.

8. In a sander relay the combination of a sander valve shiftable from a limiting sanding position through an intermediate clean-out position to an opposite limiting running position in which sanding is suspended; a movable abutment connected to shift said valve in reverse directions between said limiting positions; means forming a working space on one side of said abutment; force developing means associated with said abutment for biasing said abutment and valve toward running position when said Working space is charged with fluid under a normal ressure and toward sanding position when said pressure is substantially reduced; a delay chamber; means for charging said delay chamber with pressure fluid at a restricted rate; primary controlling means normally connecting said Working space and chamber, but operable to isolate them from each other and connect the working space to exhaust; flow restricting means for limiting the rate of such exhaust; a timing chamber; secondary controlling means normally connecting the timing chamber to exhaust, but operable to close said exhaust and connect the timing and delay chambers together; and flow restricting means having a flow capacity exceeding the charging rate to the delay chamber and controlling the last named connection.

9. In a sanding system, the combination of a sanding air supply reservoir; a sanding relay supplied with air thereby; a brake controlling valve device having a reservoir charging connection; a braking air supply reservoir connected with said charging connection to be charged thereby; a charging connection from said braking air reservoir to said sanding air reservoir; and an intercepting valve controlled by said brake controlling valve device and controlling the last named charging connection.

10. In a sanding system, the combination of a sanding air supply reservoir; a sanding relay supplied with air thereby; a brake control-ling valve device having a reservoir charging conn'ection; a braking air supply reservoir connected with said charging connection to be charged thereby; a charging connection from said braking air reservoir to said sanding air reservoir; an intercepting valve in the last named charging connection; and means associated with said brake controlling valve device and serving during a brake application to close said intercepting valve.

11. In a sanding system, the combination of a sanding air supply reservoir; a sanding relay supplied with air thereby; a brake controlling valve device having a reservoir charging connection;

a braking air supply reservoir connected with said charging connection to be charged thereby; a charging connection from said braking air reservoir to said sanding air reservoir; an intercepting valve in the last named charging connection; and means con-trolled by the brake controlling valve device for simultaneously closing said intercepting valve and actuating said relay.

12. In a sanding system, the combination of a sanding air supply reservoir; a sanding relay supplied with air thereby; a brake controlling valve device having a reservoir charging connection; a braking air supply reservoir connected with said charging connection to be charged thereby; a charging connection from said braking air reservoir to said sanding air reservoir; an intercepting valve in the last named charging connection; means rendered effective by the brake controlling valve device during a brake application to close said intercepting valve; independent means effective in the brake applying position of said brake controlling valve device to actuate said relay.

13. In a sanding system, the combination of a sanding air supply reservoir; a sanding relay supplied with air thereby; a brake controlling valve device having a reservoir charging connection; a braking air supply reservoir connected with said charging connection to be charged thereby; a charging connection from said braking air reservoir to said sanding air reservoir; an intercepting valve in the last named charging connection; means rendered effective by the brake controlling valve device during a brake application to close said intercepting valve; independent means efiective in the brake applying position of said brake controlling valve device to actuate said rclay; and means operable independently of said brake controlling valve device to actuate said relay.

14. The combination of a normally charged brake pipe extending through a train; brake control valves capable of operating on the automatic principle connected therewith at intervals; brake pipe venting means at intervals throughout the train; a sander circuit extending throughout the train; switch means for energizing and deenergizing said sander circuit; and a plurality of sanding relay units each associated with a corresponding brake control valve, and comprising a sander valve having a sanding position and a running position in which sanding is suspended, a movable abutment connected to shift said valve between said positions, means forming a working space at one side of said abutment, force developing means associated with said abutment for biasing the abutment and valve towards running position when said Working space is charged with fluid under pressure above a definite value and towards sanding position when said pressure is substantially reduced, a delay chamber, means for charging said delay chamber with pressure fluid at a restricted rate, primary controlling means for normally connecting said working space and said delay chamber but operable to isolate them from each other and connect the working space to exhaust, electric means included in said sander circuit for actuating said primary controlling means, a timing chamber, secondary controlling means normally connecting the timing chamber to exhaust but operable to close said exhaust and connect the timing and delay chambers together, and means rendered effective by emergency response of said brake control valve to render said secondary controlling means active.

15. The combination of a normally charged brake pipe extending through a train; brake control valves capable of operating on the automatic principle connected therewith at intervals; brake pipe venting means at intervals throughout the train; a sander circuit extending throughout the train; switch means for energizing and deenergizing said sander circuit, means responsive to an emergency reduction of brake pipe pressure for actuating said switch means; and a plurality of sanding relay units each associated with a corresponding brake control valve, and comprising a sander valve having a sanding position and a running position in which sanding is suspended, a movable abutment connected to shift said valve between said positions, means forming a working space at one side of said abutment, force developing means associated with said abutment for biasing the abutment and valve towards running position when said working space is charged with fiuid under pressure above a definite value and towards sanding position when said pressure is substantially reduced, a delay chamber, means for charging said delay chamber with pressure fluid at a restricted rate, primary controlling means for normally connecting said working space and said delay chamber but operable to isolate them from each other and connect the working space to exhaust, electric means included in said sander circuit for actuating said primary controlling means, a timing chamber, secondary controlling means normally connecting the timing chamber to exhaust but operable to close said exhaust and connect the timing and delay chambers together, and means rendered efiective by emergency response of said brake control valve to render said secondary controlling means active.

16. The combination of a normally charged brake pipe extending through a train; brake control valves capable of operating on the automatic principle connected therewith at intervals; brake pipe venting means at intervals throughout the train; a sander circuit extending throughout the train; switch means for energizing and deenergizing said sander circuit; means responsive to an emergency reduction of brake pipe pressure for actuating said switch means, timing means associated with said actuating means; and a plurality of sanding relay units each associated with a corresponding brake control valve, and comprising a sander valve having a sanding position and a running position in which sanding is suspended, a movable abutment connected to shift said valve between said positions, means forming a working space at one side of said abutment, force developing means associated with said abutment for biasing the abutment and valve towards running position when said working space is charged with fluid under pressure above a definite value and towards sanding position when said pressure is substantially reduced, a delay chamber, means for charging said delay chamber with pressure fiuid at a restricted rate, primary controlling means for normally connecting said working space and sand delay chamber but operable to isolate them from each other and connect the working space to exhaust, electric means included in said sander circuit for actuating said primary controlling means, a timing chamber, secondary controlling means normally connecting the timing chamber to exhaust but operable to close said exhaust and connect the timing and delay chambers together, and means rendered effective by emergency response of said brake control valve to render said secondary controlling means active.

17. The combination of a normally charged brake pipe extending through a train; brake control valves capable of operating on the automatic principle connected therewith at intervals; brake pipe venting means at intervals throughout the train; a sander circuit extending throughout the train; switch means for energizing and deenergizing said sander circuit; manual actuating means for said switch means; automatic actuating means for said switch means; timing means for sustaining the action of both said switch actuating means; and a plurality of sanding relay units each associated with a corresponding brake control valve, and comprising a sander valve having a sanding position and a running position in which sanding is suspended, a movable abutment connected to shift said valve between said positions, means forming a working space at one side of said abutment, force developing means associated with said abutment for biasing the abutment and valve towards running position when said working space is charged with fluid under pressure above a definite value and towards sanding position when said pressure is substantially reduced, a delay chamber, means for charging said delay chamber with pressure fluid at a restricted rate, primary controlling means for normally connecting said working space and said delay chamber but operable to isolate them from each other and connect the working space to exhaust, electric means included in said sander circuit for actuating said primary controlling means, a timing chamber, secondary controlling means normally connecting the timing chamber to exhaust but operable to close said exhaust and connect the timing and delay chambers together, and means rendered effective by emergency response of said brake control valve to render said secondary controlling means active.

18. The combination of a normally charged brake pipe extending through a train; brake control valves capable of operating on the automatic principle connected therewith at intervals; brake. pipe venting means at intervals throughout the train; a sander circuit extending throughout the train; switch means for energizing and deenergizing said sander circuit; manual actuating means for said switchmeans; automatic actuating means for said switch means; timing means for sustaining the action of both said switch actuating means; manually operable means for terminating the action of said timing means; and a plurality of sanding relay units each associated with a corresponding brake control valve, and comprising a sander valve having a sanding position and a running position in which sanding is suspended, a movable abutment connected to shift said valve between said positions, means forming a working space at one side of said abutment, force developing means asso ciated with said abutment for biasing the abutment and valve towards running position when said working space is charged with fluid under pressure above a definite value and towards sanding position when said pressure is substantially reduced, a delay chamber, means for charging said delay chamber with pressure fluid at a restricted rate, primary controlling means for normally connecting said working space and said delay chamber but operable to isolate them from each other and connect the working space to exhaust, electric means included in said sander circuit for actuating said primary controlling means, a timing chamber, secondary controlling means normally connecting the timing chamber to exhaust but operable to close said exhaust and connect the timing and delay chambers together, and means rendered eiTective by emergency response of said brake control valve to render said secondary controlling means active.

19. In a sander relay the combination of a sander valve having a sanding position, and a running position in which sanding is suspended; a movable abutment connected to shift said valve between said positions; means forming a working space at one side of said abutment; force developing means associated with said abutment for biasing said abutment and valve toward running position when said working space is charged with fluid under pressure above a definite value and toward sanding position when said pressure is substantially reduced; means for supplying pressure fluid to said working space at a restricted rate; a timing chamber; controlling means normally connecting the timing chamber to the exhaust but operable to close said exhaust and connect the timing chamber with said working space; and means for operating said controlling means.

20. In a sander relay the combination of a sander valve having a sanding position, and a running position in which sanding is suspended; a movable abutment connected to shift said valve between said positions; means forming a working space at one side of said abutment; force developing means associated with said abutment for biasing said abutment and valve toward running position when said working space is charged with fluid under pressure above a definite value and toward sanding position when said pressure is substantially reduced; means for supplying pressure fluid to said working space at a restricted rate; a timing chamber; controlling means normally connecting the timing chamber to the exhaust but operable to close said exhaust and connect the timing chamber with said working space; pressure operated means for actuating said controlling means, and a brake controlling valve device connected with said pressure operated means and arranged to deliver pressure thereto as an incident to the brake applying function of said brake controlling valve device.

21. In a sander relay the combination of a sander valve shiftable from a limiting running position in which sanding is suspended through an intermediate clean-out position to an opposite limitin sanding position; a movable abutment connected to shift said valve in reverse directions between said limiting positions; means forming a working space on one side of said abutment; force developing means associated with said abutment for biasing said abutment and valve toward running position when said working space is charged with fluid under a normal pressure and toward sanding position when said pressure is substantially reduced; means for charging said working space with pressure fluid at a restricted rate; a timing chamber; control- U ling means normally connecting the timing chamber to exhaust but operable to close said exhaust and connect the timing chamber with said working space; flow restricting means having a flow capacity exceeding the charging rate to the working space and controlling the last named connection; and means for actuating said controlling means.

22. The combination of a sanding unit having a sanding air connection and a clean-out air connection, a pair of pressure motor operated air valve mechanisms, one associated with each connection and each having a normal position in which it vents the corresponding connection and an active position which it assumes when its motor is subjected to pressure and in which it opens a large capacity supply to the corresponding connection and closes said exhaust; a pilot slide valve shiftable from a running position, in which it relieves pressure from the motors of both said air valve mechanisms, through an intermediate position in which it admits pressure at least to the motor of the clean-out air valve mechanism, to a limiting position in which it admits pressure at least to the motor of the sanding air valve mechanism alone; a movable abutment connected to shift said pilot valve in reverse directions between said limiting positions; means forming a working space on one side of said abutment; force developing means associated with said abutment for biasin the abutment and pilot valve toward said running position when said Working space is charged with fluid under normal pressure and toward said sanding position when said pressure is substantially reduced; means for chargingsaid working space with pressure fiuid at a restricted rate; a timing chamber; controlling means normally connecting the timing chamber to exhaust but operable to close said exhaust and connect the timing chamber and working space together; flow restricting means having a flow capacity exceeding the charging rate to the working space and controlling the last named connection; and means for operating said controlling means, the parts being so arranged that the pilot valve shifts between its limiting positions in both directions at a gradual rate and the motor operated valve mechanisms respond to establish rapid flows which are timed by the pilot valve.

23. The combination of a sanding unit having a sanding air connection and a clean-outair connection, a pair of pressure motor operated air valve mechanisms, one associated with each connection and each having a normal position in which it vents the corresponding connection and an active position which it assumes when its motor is subjected to pressure and in which it opens a large capacity supply to the corresponding connection and closes said exhaust; a pilot slide valve shiftable from a limiting running position, in which it relieves pressure from the motors of both said air valve mechanisms, through an intermediate position in which it admits pressure at least to the motor of the clean-out air valve mechanism, to a limiting position in which it admits pressure fluid to the actuating motor of the sanding air valve mechanism alone; a movable abutment connected to shift said pilot valve in reverse directions between said limiting positions; means forming a working space on one side of said abutment; force developing means associated with said abutment for biasin the abutment and pilot valve toward said running position when said working space is charged with fluid under normal pressure and toward said sanding position when said pressure is substantially reduced; a delay chamber; means for charging said delay chamber with pressure fluid at a restricted rate; primary controlling means normally connecting said working space and delay chamber but operable to isolate them from each other and connect the working space to exhaust; flow restrictin means for limiting the rate of such exhaust; a timing chamber; secondary controlling means normally connecting the timing chamber to exhaust but operable to close said exhaust and connect the timing and delay chambers together; and flow restricting means having a flow capacity exceeding the charging rate to the delay chamber and controlling the last named connection.

24. In a sander relay the combination of a sander valve having a sanding position, and a running position in which sanding is suspended; a movable abutment connected to shift said valve between said positions; means forming a working space at one side of said abutment; force-developin means associated with said abutment for biasing said abutment and valve toward running position when said working space is charged with fluid under pressure above a definite value and toward sanding position when said pressure is substantially reduced; a delay chamber; means for charging said delay chamber with pressure fluid at a restricted rate; and controlling means normally connecting said working space with said delay chamber, but operable to isolate them from each other and connect the working space to exhaust.

25. In a sander relay the combination of a sander valve having a sanding position, and a running position in which sanding is suspended; a movable abutment connected to shift said valve between said positions; means forming a working 15 space at one side of said abutment; force-developing means associated with said abutment for biasing said abutment and valve toward running position when said working space is charged with fluid under pressure above a definite value and toward sanding position when said pressure is substantially reduced; a delay chamber; means for charging said delay chamber with pressure fluid at a restricted rate; and controlling means normally connecting said working space with said delay chamber, but operable to isolate them from each other and establish a restricted exhaust flow path from said working space.

CHARLES A. CAMPBELL. 

